Manually operated hooks or clasps are found in the prior art that operate using a spring that holds the hook closure closed when the spring is extended. When springs are extended they exert little or no force, meaning that the hook closure is held closed with little or no force. This makes it relatively easy to slightly open the closure to enable the hooked item to slip off the hook. When the closure is opened more completely, the spring exerts progressively more force making the closure harder to open as the spring is compressed. Thus, in prior art hooks of this type, it is harder to purposely open the hook to attach or secure something than it is to accidentally lose something off the hook.
The prior art design tends to cause injuries in that the compressed spring can snap forward unexpectedly injuring the user. In addition, the protruding knob used to pull and hold open the spring is often uncomfortable or even painful to operate.
U.S. Pat. No. 7,441,424 to Saitoh, et al. discloses a clamp that opens similar to a scissors with two arms connected by an off-center pivot pin. The two opposing long arms include a pin to hold a security tag or materials while each of the two short arms includes a magnet of opposing polarity which together hold the clamp in the closed position. The clamp has the disadvantage of not securing an item on the arm and not enabling secure movement of the secured item when the disclosed clamp is closed.
U.S. Patent Application Publication No. 2007/0209168 to Dietz teaches a magnetic spring clip that is attached to an instrument such as a pen or penlight. However, the clip requires that a magnet be in the instrument that is held by the clip thereby introducing a limitation to its usefulness in that nonmagnetic devices cannot be securely held by the clip.
U.S. Patent Application Publication No. 2008/0250615 to Emenheiser teaches a retainer apparatus in the form of a modified hook having a closure that is held in the open position by a magnet. The retainer includes a biasing device to move the closure into the closed position. The Emenheiser retainer requires a trigger to activate the biasing device which, similar to other prior art discussed above, has reduced force to keep the retainer in the closed position. In addition, the use of a trigger mechanism increases the possibility of injury caused by the inadvertent activation of the biasing trigger.
In addition, as mentioned above, the clasps and hooks currently in the field are easily opened accidentally because of the lack of positive force holding the closure in the closed position. The main impediment to overcoming this deficiency is devising a simple structure that not only provides positive closing force to the closure, but can still be easily opened without excessive force and require a minimum number of parts.
Thus, it can be seen there is a need in the field for a hook closure that is easily opened, utilizes a positive force to hold a clasp or hook in the closed position around a hook type of device, and prevents or reduces accidental opening of the clasp or hook.